The invention relates to a synthetic material which is particularly useful for processing feedstock having large organic molecules, either as a catalyst or as a sorbent.
The processing of large organic molecule-containing feedstocks such as heavy hydrocarbons, fine chemicals, pharmaceutical products and the like involving catalysts or adsorbents is typically inefficient and expensive due to the lack of catalyst materials with appropriate qualities. A significant limitation on conventionally known active agents is the lack of sufficient pores of appropriate size in the catalyst or adsorbent to carry out the desired process.
Typically, heavy hydrocarbons are processed using amorphous materials having pore volumes lower than 0.1 cc/g, which pore volume is distributed over a wide range of pore diameters, typically ranging between 20 to 1,000 angstrom (.ANG.) in diameter. Due to the large range and high upper end of the pore diameter of this material, the pore volume is lower than would be desirable. Furthermore, these materials possess low-activity sites where activity is defined in terms of number of molecules converted per unit of time, thereby limiting their effectiveness as promoters in conversion to desirable products.
Due to the foregoing limitations, heavy hydrocarbons are occasionally processed using zeolite catalysts which are not ideal due to the pore diameter formed in crystalline microporous aluminosilicates such as zeolite. Because of the small pore diameter, only active sites on the particle exterior of the zeolite are useful for processing such heavy hydrocarbons. This results in the use of large quantities of the zeolite, thereby significantly increasing the catalyst cost involved with the process, and decreasing the profitability of same.
Attempts have been made to improve the accessibility to large hydrocarbons of the active sites in a zeolite material. One method which has been industrially applied has been the dealumination of the material, for example by steam or contact with SiCl.sub.4. By extracting aluminum from the zeolite framework, a portion of the crystal structure collapses giving rise to holes ranging in diameter from 10 .ANG. to 1,000 .ANG.. Although this procedure does provide some degree of larger pore volume in zeolites, several disadvantages are inherent. First, several post-synthesis steps are required, which result in the waste of a portion of the original starting zeolite material, thereby making the synthesis process more complicated and expensive. In addition, amorphous alumina particles resulting from the extraction process are left on the surface on the mesoporous channels, hindering or even blocking the diffusion of reactants and products. Further, this procedure does not selectively generate pores of a particular desired size. Rather, a random distribution of large pores are generated, most of which are larger than 100 .ANG. in diameter. Because of this, dealuminated zeolites have limited use in catalytic processes that, based on size exclusion principles, must essentially yield a desired large organic product.
Available sorbents for separation of large molecules from feedstocks also have important technological limitations. They are constituted by amorphous materials, with low density of sorption sites.
It is clear, therefore, that the need remains for an improved material, for use either as a catalyst or as a sorbent, in processing, converting and/or purifying feedstocks having large organic molecules such as heavy hydrocarbons and the like.
It is therefore the primary object of the present invention to provide a synthetic material having microporous crystalline walls, accessible through a high volume of mesoporous channels of desired and controlled pore diameter sizes and distributions.
It is a further object of the present invention to provide a process for preparing the material of the present invention wherein the material has microporous crystalline walls having micropore sized pore volume and is provided with a high mesopore sized pore volume in a narrow pore size distribution.
It is still another object of the present invention to provide a process for treating a feedstock having large organic molecules with the material of the present invention used as a catalyst so as to provide conversion and transformation of the feedstock into more valuable products, at high rates of conversion, and with high selectivity.
It is still another object of the present invention to provide a process for purification of a mixture of organic compounds so as to selectively remove one or more components from this mixture by adsorption onto the material of the present invention.
Other objects and advantages of the present invention will appear hereinbelow.